Best open-source alternatives to Microsoft Teams

Rocket.Chat is an open-source communications platform aimed at organizations that need secure, customizable collaboration tools. It supports team messaging and real-time conversations for internal coworkers as well as external communication with customers, citizens, or partner companies. The project is designed for self-hosted, cloud, and air-gapped deployments, making it suitable for regulated or high-security environments. It also includes security and governance features such as identity management, end-to-end encryption, and role- and attribute-based access control, while offering extensibility through a marketplace, Apps-Engine, and external integrations.

Mattermost is an open core collaboration platform designed for teams that want to self-host their communication and workflow stack. It provides a web-based interface and native clients for desktop and mobile, and is positioned for use cases such as DevSecOps, incident resolution, and IT service desk operations. The project is the primary source for core platform development and is implemented in Go and React. The software runs as a single Linux binary and depends on PostgreSQL for storage. The README emphasizes deployment flexibility, with installation paths for Docker, Ubuntu, tar archives, Kubernetes, and Helm. It also points users to product and developer documentation, and highlights a broad integration surface including webhooks, slash commands, drivers, web services, apps, and plugins.

Zulip is an open-source team chat platform designed to help organizations manage both real-time and asynchronous communication in a more structured way than traditional chat apps. Its signature feature is topic-based threading, which keeps conversations organized and makes it easier for distributed teams to follow multiple discussions without losing context. The project is aimed at teams, open-source communities, and other organizations that need productive group communication. The README highlights self-hosting on Ubuntu or Debian Linux, deployment via Docker, and hosted cloud options through Zulip Cloud. It also emphasizes a large contributor community and extensive documentation for both code and non-code contributions, suggesting a mature project with a broad user and developer ecosystem.

Neko is a self-hosted virtual browser and desktop streaming project designed to run inside Docker and deliver the session to users over WebRTC. It is aimed at people who want a private, secure, and shareable browser environment, including developers, teams, presenters, and users who need a persistent or isolated browsing session. The project emphasizes collaborative use: multiple participants can access the same session, interact with the browser in real time, and use it for watch parties, teaching, support, brainstorming, or remote presentations. Beyond browsers, it can stream other Linux applications or even a full desktop environment, and it also supports use cases like session broadcasting, recording, and browser automation.

Tinode is an instant messaging platform intended as a modern, open replacement for XMPP-style federated chat systems. It provides a backend written in Go and clients for web, Android, iOS, and a scriptable command-line interface. The project is aimed at teams or individuals who want a self-hostable messaging stack with mobile and browser access. The server supports messaging, calls, channels, access control, and multi-device synchronization, while also offering administration tooling and support for custom authentication backends. It can be deployed with different database backends and uses JSON/websocket or protobuf/gRPC transports. The README also points to public demo and sandbox services for trying the system before self-hosting.

screego/server is a screen-sharing service aimed at developers who need clearer, faster remote viewing than typical corporate meeting tools provide. It is positioned as a lightweight addition to existing collaboration software, focused specifically on screen sharing rather than broader conferencing or chat features. The project emphasizes simple deployment and practical network handling. The README highlights support for multi-user screensharing, secure transfer over WebRTC, low latency, high resolution, and an integrated TURN server for NAT traversal. It can be installed either with Docker or as a single binary, and the project provides a public demo instance and documentation for setup and configuration.

ejabberd is an open-source realtime communications platform built on Erlang/OTP. It is designed for administrators and organizations that need a scalable backend for messaging and related network services, and it bundles an XMPP server together with MQTT broker and SIP service functionality. The project can be installed from source, via operating-system packages, through Homebrew, or by using published Docker container images and release installers. Its README points users to the ejabberd documentation site for setup and administration guidance, and to separate developer documentation for contributors. The project also notes a commercial offering and support path through ProcessOne, including a Business Edition and cloud-hosted service.

The Lounge is a self-hosted web IRC client intended for people who want a persistent, browser-based way to stay connected to IRC networks. It is positioned as a modern alternative to traditional IRC clients, with features such as push notifications, link previews, and message markers to make IRC feel more contemporary. It is aimed at users who want their IRC presence to persist across devices and sessions. The README emphasizes that it stays connected while the user is offline, works across platforms wherever Node.js runs, and provides a responsive interface for desktop, smartphone, and tablet use. The project also documents a source-based installation path for development and links to a Docker-based deployment option for stable releases.

MiroTalk P2P is an open-source, self-hosted video conferencing system for people and teams who want real-time communication under their own control. It emphasizes peer-to-peer WebRTC sessions, unlimited rooms, and end-to-end privacy, making it suitable for organizations that need a private alternative to cloud-only meeting platforms. The project can be run locally from source or deployed with Docker and Docker Compose. Its feature set includes high-resolution video, screen sharing, recording, chat, whiteboarding, file sharing, OIDC authentication, room passwords, host protection, and integrations such as Slack, Mattermost, and embeddable widgets. The README also highlights a REST API and self-hosting documentation for customization and integration.

Campfire is a web-based chat application designed for teams or groups that need a self-hosted messaging system. It provides familiar collaboration features such as rooms, direct messages, file attachments, search, mentions, and push notifications, along with access controls for rooms. The project is positioned as a single-machine deployment that bundles the web application, background jobs, caching, file serving, and SSL into one Docker image. The README also indicates that Campfire is intended to be administered locally by the operator, who creates an initial admin account on first launch. It is single-tenant, meaning separate customer groups would require separate instances rather than isolated workspaces within one deployment. The included API support suggests it can be extended for bot integrations and other external automation.